From: Eric Dumazet <eduma...@google.com> Date: Wed, 12 Jun 2019 09:52:25 -0700
> Using tcpdump (or other af_packet user) on a busy host can lead to > catastrophic consequences, because suddenly, potentially all cpus > are spinning on a contended spinlock. > > Both packet_rcv() and tpacket_rcv() grab the spinlock > to eventually find there is no room for an additional packet. > > This patch series align packet_rcv() and tpacket_rcv() to both > check if the queue is full before grabbing the spinlock. > > If the queue is full, they both increment a new atomic counter > placed on a separate cache line to let readers drain the queue faster. > > There is still false sharing on this new atomic counter, > we might in the future make it per cpu if there is interest. Series applied.
